The invention herein relates to a keratome having a cutter head with a suspended stabilized reciprocating blade, an improved suction ring accepting an applanator and with entrance and cutting guideways for presenting and applying the cutter head and its suspended blade to the cornea, drive means for automated translation of the cutter head, and blade insertion cooperating with the cutter head.
A keratome is an instrument used in ophthalmic surgery and, more particularly, in surgery to reshape the cornea for vision correction. A keratome incises a generally spherical segment of the cornea except for a connecting hinge. The cornea segment is lifted and held aside while the exposed truncated cornea surface is shaped for vision correction. Thereafter, the spherical cornea segment is repositioned to cover the shaped, truncated cornea surface. The cornea segment heals to the shaped surface, resulting in a reshaped cornea that acts as a corrective lens.
It will be appreciated that a keratome must achieve an accurately positioned, surgically precise cut with minimal tissue damage to enhance the healing process. Further, the cut must remain uncontaminated, also to aid the healing process and avoid irritation and infection.
In accurately positioning and performing a cornea cut, it is known to use a suction ring as an interface with the eye. Suction is used to temporarily secure the suction ring to the eye in a desired position. Typically, a suction ring is secured to the sclera, near the periphery of and surrounding the cornea.
It is also desirable to measure the cornea and coordinate the extent of the incision with the size of cornea in order to remove a properly sized cornea segment and to provide an appropriate hinge in conjunction with the excised cornea segment.
It is also known to apply a cutting instrument with the suction ring. Thus, the suction ring positions and presents the cutting instrument with respect to the cornea. Clearly, if any slippage or disengagement of the suction ring occurs, a correspondingly inaccurate cut may also occur. Present suction rings occasionally do experience slippage or disengagement, and it is believed this occurs because of a poor interface with the surface of the sclera resulting in loss of suction or uneven suction along various segments of the ring. Currently, engagement of a cutting instrument with a suction ring is often difficult to achieve, because the engagement must be precise, making the engagement difficult to initiate.
Precision of the cornea cut requires proper positioning of a cutting instrument with respect to the cornea, which is achieved by the location and secure attachment of the suction ring, and also requires a very smooth operating cutting blade. Cutting instruments often use a reciprocating cutting blade to achieve a smooth, precise incision. Any flutter in the operation of the reciprocating cutting blade can cause a somewhat ragged incision, with consequent difficulties in replacing the cornea segment and smooth healing thereof.
The cornea cut must also remain uncontaminated, because any foreign matter in the incision may become encapsulated and cause irritation and possible infection. Cutting instrument designs which support a cutting blade on a bearing surface adjacent the area of the incision increase the risk of contamination. Contact between the cutting blade and the bearing surface creates friction and wear. This not only heats the cutting blade, but also sloughs off microscopic metal wear particles. These may lodge in the cornea incision, with undesirable effect.
It is also desirable to translate the cutting instrument across the cornea in a smooth manner and to reliably stop the translation of the cutting instrument at the furthest extent of the cut. Non-damaging withdrawal of cutting instrument is also desirable.
There is also a need to quickly and easily load blades into the cutting instrument, and to remove blades after use.
Therefore, there is a need for a keratome including a suction ring that easily, accurately and securely positions a cutting instrument with respect to the cornea and that provides a surgically precise, uncontaminated incision of a cornea segment. There is an additional need for improved automation in making the incision.
Accordingly, it is a principal object of the invention herein to provide a keratome for ophthalmic surgery.
It is an additional object of the invention herein to provide a keratome that achieves accurate and secure engagement with the eye.
It is another object of the invention to provide a keratome that facilitates accurate, pre-cut measurement of the cornea.
It is also an object of the invention to provide a keratome including a cutting instrument that is easily and accurately engageable with a suction ring secured to the eye.
It is an additional object of the invention to provide a keratome with automated translation of a cutting instrument across a suction ring.
It is a further object of the invention to provide a keratome that achieves an accurate and smooth cut.
It is another object of the invention to provide a keratome that avoids contamination of the incision made on the cornea.
It is also an object of the invention to provide a keratome with simple and efficient changing of the blade in a cutting instrument.
According to general aspects of the invention herein, a keratome generally comprises a suction ring and a cutting instrument having a cutter head guided into precision sliding engagement with the suction ring, the cutter head including a suspended, reciprocating blade. An applanator is receivable on the suction ring for measuring the segment of cornea to be cut, and the cutting instrument is adjustable or preset for length of cut.
Also according to aspects of the invention, a keratome generally comprises a cutting instrument having a cutter head including a reciprocating blade with a cutting edge extending below a sole surface, and a suction ring. The suction ring includes an eye ring adapted to be secured to an eye by suction and defines a cornea aperture presenting the cornea of the eye for cutting a cornea segment. The suction ring furthers includes a shoe from which the eye ring extends, the shoe defining a cutting guideway configured for receiving the cutter head in precision mating sliding engagement for passing the cutting edge of the cutter blade over the cornea aperture and thereby incising a cornea segment. The shoe further defines an entrance guideway extending from and generally aligned with the cutting guideway, the entrance guideway configured for receiving the cutter head in orienting sliding engagement positively positioning the cutter head into the aforesaid precision mating sliding engagement in the cutting guideway.
According to additional aspects, the cutter head defines two tongues extending downwardly at the edges of its sole surface, and the cutting guideway includes two guide grooves respectively receiving the tongues. The cutting guideway guide grooves are fully defined at the transition between the entrance guideway and the cutting guideway. According to further aspects, the entrance guideway is partially defined by a guide hoop of the shoe, and the cutter head is cooperatively shaped to enter the guide hoop and progressively orient the cutter head for entry to the cutting guideway. The guide hoop is preferably positioned substantially at the transition between the entry guideway and the cutting guideway. Also, according to further aspects, the entrance guideway includes curbs upstanding along the marginal edges of an entrance ramp portion of the shoe for generally aligning the cutter head with the guide hoop, the shoe defines side rails extending from the guide hoop, and the cutter head has side rail pockets slidingly receiving the side rails. Thus, there are multiple points of contact between the cutter head and the shoe defining the entrance guideway, serving to align the cutter head for sliding movement in the cutting guideway. The foregoing configurations of the cutter head and suction ring provide easy engagement and accurate positioning of the cutter head within the suction ring.
Referring to another aspect, the suction ring includes a handle and the handle is preferably positioned opposite the entrance guideway of the suction ring, for manual stabilization of the suction ring and coordination of the suction ring and cutting instrument during introduction of the cutting instrument.
According to still other aspects in the invention, a suction ring includes an eye ring defining a cornea aperture and a shoe, and the shoe defines a socket for receiving and positioning an applanator with a measuring surface in contact with a cornea of an eye presented through the cornea aperture, for measuring the size of the cornea to be incised. Cooperating stop means are provided between the suction ring and cutting instrument for adjusting the extent of the incision according to the applanator measurement of the cornea.
According to a still further aspect of the invention, the cutting instrument includes a stop which butts against the suction ring at a desired extent of incision. The stop is preferable a rotatable collar adjustably presenting one of a plurality stops for selectively setting different extents of incision.
According to additional aspects, a suction ring includes an eye ring with outer and inner contact surfaces shaped to engage the eye, and a suction channel defined between the inner and outer contact surfaces. The suction channel additionally defines a secondary distribution channel and a suction conduit opens to the suction channel and the secondary distribution channel. The secondary distribution channel ensures delivery and equalization of suction about the eye ring for secure attachment to the eye.
Also according to aspects of the invention herein, the cutting instrument includes a cutter head having a blade assembly. The blade assembly includes a metal cutting blade mounted to and extending from a blade holder to a cutting edge. The blade holder is preferably fabricated of a polymer, such as nylon. The blade holder defines a drive track transverse to the cutter blade and its cutting edge. The cutter head further defines a blade cavity generally accommodating and supporting the blade holder for reciprocal sliding movement. The cutter head defines a blade slot accommodating the cutting blade and extending to a blade opening from a foot of the cutter head, adjacent which the cutting edge is deployed for incising the cornea. The cutting blade is suspended with respect to and does not contact the cutter head. The cutter head defining the blade cavity is preferably of unitary, one-piece construction, but may also be comprised of a base and a cap together defining the blade cavity.
The blade cavity includes a guide bar cooperating with a guide slot formed in the blade holder. According to one aspect of the invention, the guide is a linear guide bar received in the guide groove formed in the blade holder, and configured for thin line contact between the guide bar and the guide groove. According to another aspect of the invention, the guide bar is comprised of two spaced apart post projections received in the guide slot, which is parallel to the cutting edge of the blade.
According to additional aspects of the invention, the blade cavity defines one of a guide slot or guide bar, and the blade holder defines the other of the guide slot or guide bar, the guide bar extending into the guide slot in closely conforming mating sliding engagement to guide and stabilize the blade holder in its reciprocal movement within the cutter head. In a more particular aspect of the invention, the cutter head defines a substantially rectangular guide bar, and the blade holder defines a substantially rectangular guide slot accommodating the guide bar. The guide slot has an incrementally smaller width than the guide bar to preload the blade holder on the guide bar. The guide bar, and additional surfaces of the blade cavity, may be treated with a lubricous coating such as a nickel/Teflon(copyright) coating, to provide smooth reciprocation.
The cutter head further includes a blade shield and foot, the foot having projecting tongues for slidingly engaging the guide grooves of the shoe portion of the suction ring. The cutter head is characterized in that it does not contact the cutting blade, which is suspended extending from the blade holder. The cutting edge of the blade extends a selected distance below a forward or toe surface of the foot to establish a uniform depth of cut.
According to one aspect of the invention, the cutter head includes a view port as part of the foot, for visually monitoring passage of the cutter head and blade over the cornea and the cut.
In some aspects, the cutting instrument further includes a handle drive, to which the cutter head is secured. The handle drive has a drive shaft extending through the cutter head and terminating in an eccentric drive pin received in the drive track of the blade holder. A handle drive turbine is used to rotate the drive shaft at high rpm, which according to one aspect of the invention is between 8,000 and 16,000 rpm, and thereby reciprocate the blade holder and blade. The drive shaft is supported on bearings and located to isolate application of the drive force to the blade holder through the drive pin, in cooperation with the cutter head.
According to further aspects, the cutting instrument is reciprocally mounted in an automated drive unit. The automated drive unit is engageable with the suction ring, and the automated drive unit has drive means for advancing the cutting instrument and its cutter head across the suction ring and for retracting the cutting instrument and cutter head after incising a cornea segment of an eye. The automated drive unit is removably secured to the suction ring and can be introduced in the suction ring after the suction ring is secured on the eye. Thus, the suction ring is attached without the bulk of the automated drive unit and its cutting instrument, and the automated drive unit and associated cutting instrument and cutter head are easily joined to the suction ring for cutting.
Also, according to aspects, the automated drive unit has a threaded shaft and worm gear and includes a motor powering the threaded shaft to translate the cutting instrument and cutter head. The motor may be an electric motor, and an electrical spike at the limit of travel may be used to reverse the direction of the cutting instrument and cutter head for automated withdrawal. The cutting instrument may be inactivated during withdrawal.
According to other aspects, the cutting instrument includes a tubular body with a motor and a cutter head, and the cutter head mounts to the tubular body by means of a mounting shank and a bayonet shaped groove which positively orients the cutter head with respect to the tubular body. The bayonet style groove also provides for quick mounting and dismounting of the cutter head. According to additional aspects of the invention, the motor of the cutting instrument is connected to a drive shaft for reciprocating a cutter blade in the cutter head, the connection being achieved by a coupling including a drive coupling member having ears received in mating slots of a positioning coupling member, and a positioning coupling member having pointed ears for guiding the drive ears into the mating slots.
According to further aspects of the invention, the keratome is provided with a blade insertion tool which includes a shaft retractor for retracting the drive pin of a blade drive shaft from the cutter head blade cavity to provide clearance for inserting the blade, and an injector for inserting a cutter blade into the blade cavity and for displacing a used cutter blade out of the blade cavity.
Other objects, aspects and features of the invention will in part be understood by those skilled in the art and will in part appear from a perusal of the following description of the preferred embodiments and the claims, taken together with the drawings.